About the Image Upscaler
Our Image Upscaler is a free online tool that enlarges your images up to 4× their original resolution — no account, no watermark, no file size restrictions beyond 20 MB.
How It Works
When you upload an image, it is sent to our processing server where we apply Lanczos resampling (also called Lanczos3 or sinc resampling) — a mathematically optimal algorithm for image enlargement that minimises blurring and aliasing compared to simpler methods like bilinear or nearest-neighbour interpolation.
Lanczos resampling works by computing a weighted average of the surrounding pixels using a sinc-based kernel. This preserves sharp edges and fine detail better than other CPU-based methods, making it the standard algorithm used in professional tools like Photoshop, GIMP, and FFmpeg.
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Scale Factor Guide
- 1.5× — subtle enlargement; good for fixing slightly undersized images
- 2× — the most common choice; doubles width and height (4× pixels total)
- 3× — for printing small photos at larger sizes
- 4× — maximum enlargement; best results on images with sharp lines (screenshots, logos, illustrations)
Privacy
Your uploaded image is sent to our server for processing. It is used solely to perform the upscaling operation and is immediately deleted after the result is returned to your browser. We never store, log, or share your images. See our full Privacy Policy.
Frequently Asked Questions
Is there a file size limit?
Yes: 20 MB per image and 4096×4096 pixels maximum input resolution.
What image formats are supported?
JPEG, PNG (including transparent PNGs), WebP, and GIF (first frame only).
Will the upscaled image look blurry?
Lanczos resampling produces the sharpest results of any CPU-based method, but no algorithm can create detail that wasn't in the original image. Very low-resolution originals (under 100px) will still look soft at 4×. Use 2× for best results on small images.
Is this different from AI upscaling?
Yes. AI upscaling (e.g. Real-ESRGAN, Waifu2x) uses a neural network trained on millions of images to hallucinate realistic detail that wasn't in the original. This tool uses classical Lanczos resampling which is mathematically deterministic and faster. AI upscaling produces better results for photos but requires significantly more computing power.
Can I use the upscaled images commercially?
Yes — we claim no rights over your images. The copyright of the output belongs to you. However, you are responsible for ensuring you own the rights to the original image.